The present invention relates to a diaphragm pump, particularly a fuel diaphragm pump with a working chamber and a chamber separated from the working chamber by the diaphragm and having a compression spring. This chamber is connected to the intake pipe of an internal combustion engine downstream of the throttle flap of a carburetor for introducing vacuum pressure. At the end of the intake stroke of the pump, the diaphragm opens a valve for atmospheric venting of the second chamber by means of a plunger.
During idling and partial load operation of an internal combustion engine having a carburetor, such a pump serves to withdraw fuel continuously from the accelerator pump of a carburetor in order to prevent vapor bubble formation, caused by heat accumulation, in the accelerator pump through this scavenging. Another application in the motor vehicle, for example, as windshield wiper pump, is conceivable.
Such a pump is known from the German Laid-Open Document 26 14 625, published Aug. 28, 1977. However, this arrangement has the disadvantage that depending on the design layout, either the intake stroke or the working stroke of the pump cannot be carried out over the full stroke since venting either takes place before the intake stroke is finished, or evacuation takes place before the working stroke is finished. Hence the delivery is unsatisfactory.
Accordingly, it is an object of the present invention to provide such a pump where the design stroke of the diaphragm is fully utilized.
Another object of the present invention is to provide a pump of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide a pump, as described, which is reliable in service and has a substantially long operating life.